CN101103638B - Wireless communication method and apparatus for optimizing access point channel selection - Google Patents

Abstract

A wireless communication method and system for optimizing channel selection for an AP. The channel selection optimization process includes four sub-processes: 1) a measurement process; 2) a candidate channel determining process; 3) a channel selection process; and 4) a channel update process. Candidate channels used for supporting communication performed by the AP are determined. The candidate channels are chosen from an allowable channel set (ACS) if a detected interference of each candidate channel is less than an established maximum allowed interference.

Description

Wireless communications method and device that optimizing access point channel is selected

Technical field

The relevant a kind of wireless communication system of the present invention.More specifically, the present invention is relevant is that an access point (AP) is selected the most appropriate operation channel.

Background technology

The condition of one wireless link at one wireless communication system running place may change at any time.Because a wireless transmission/receive unit (WTRU) is mobile, this WTRU may break away from calmly on its position or in the scope of one or more APs.

The capacity of one communication system is limited because frequency range considers sometimes.Can be limited for the frequency range capacity of the communication channel of communication system contact data, and must share in a plurality of APs and Portable WTRUs.

There are now several frameworks to be used to improve the capacity of wireless communication system.It is that this framework is wherein a kind of that channel (that is frequency) is selected, so as to allowing the one or more APs in the network select the relevant WTRUs with other of one or more channels to get in touch with.The coordination that the AP channel is selected generally is to carry out with manual mode.But it be very unpractical coordinating with manual mode that channel selects in response to each the little variation in the network configuration, because this may cause the redesign of all APs and configuration again.The problem that unauthorized frequency spectrum and external interference source also can cause manual coordination fully to solve.In addition, be difficult to by manual channel selective mode with the meeting of Channel Assignment one-tenth so that the traffic load of adjacent APs share in available channel in the mode of a maximum overall system capacity.

Existing framework is having a plurality of APs can meet with another problem in attempting to start shooting simultaneously.This situation occurs in a network, and all APs attempt making a channel at same time and select.Therefore, it can not be best that the channel of APs is selected, and does not select to include in to consider because each AP will be close to the channel of APs.

Automatically to select to avoid method and the device of the foregoing problems relevant with existing manual channel selection procedure can be very favourable to the optimization channel.

Summary of the invention

Wireless communications method and device that the channel of relevant a kind of optimization one AP of the present invention is selected.This device can be an AP and/or an integrated circuit (IC).

Channel selects optimization procedures to comprise four subprocess: a 1) measuring process; 2) a candidate channel decision process; 3) channel selection procedure; And 4) a channel renewal process.Determine the candidate channel for the communication of supporting to be undertaken by this AP.This candidate channel is that recording from a tolerable channel set (ACS) take each candidate channel disturbed and to be less than one and to have determined that maximum allows to disturb as condition and select.

Description of drawings

Below will carry that the present invention is described in detail by reference to the accompanying drawings more clearly understanding for the present invention with way of example, in the accompanying drawing:

Fig. 1 is a calcspar according to one of the present invention wireless communication system;

Fig. 2 is a flow chart according to one of one embodiment of the invention channel optimization procedures; And

Fig. 3 A Fig. 3 B Fig. 3 A and Fig. 3 B connect together, and it is a detail flowchart according to the channel selection procedure of another embodiment of the present invention.

Embodiment

Hereinafter, term " WTRU " comprises but the non-device that is confined to a subscriber equipment (UE), a mobile radio station, fixing or moving user unit, calling set or any type that other can operate in a wireless environment.

Hereinafter, term " AP " comprises but non-ly is confined to an access point, a base station, B node, site controller or the interface device of any other type in wireless environment.

Feature of the present invention can be merged in the IC or be configured in one and comprise in the circuit of a plurality of interconnecting assemblies.

As described below, the present invention can be applicable to WLAN (WLAN) technology substantially, for example be applied to substantially IEEE 802.11 and ETSI HyperLAN specification, yet also it can be applied in other limit interferences wireless system such as IEEE 802.15 and IEEE 802.16.

Fig. 1 is a calcspar according to wireless communication system 100 of the present invention.Wireless communication system 100 comprises an AP 105 and a plurality of WTRUs 110a-110n.AP 105 gets in touch with WTRUs 110a-110n by a wireless link 115 via an antenna 120.AP 105 comprises a transceiver 125, a channel selector 130, a measuring unit 135, a power controller 140, a timer 145 and a memory 150.Transceiver 125 sends signal 115a-115n and receives signal 115a-115n from this WTRUs via 120 couples of WTRUs 110a-110n of antenna.

Channel selector 130 is selected a channel that is used for each WTRU 110a-110n contact.Measuring unit 135 is measured the job parameter that is used for supporting AP 105.Measuring unit 135 is responsible for collecting, processing and the memory channel measured value, this measured value comprises but non-being confined to: channel utilization rate (that is time percentage of channel busy), the position that disturb outside (non-802.11) is accurate, the received signal strength that records from receiving package, and similar measurements.The through-put power of power controller 140 control AP 105.Timer 145 is set one or more predetermined period that AP 105 carries out some operation.Memory 150 comprises the data of record such as measurement result for AP 105 provides storage capacity.

Fig. 2 is a flow chart according to channel optimization procedures 200 of the present invention.The channel optimization refers to select the process of the optimum channel (that is frequency) that a specific AP or APs network use under the particular data transmission condition.The channel optimization can be with manual mode or automated manner and carries out, and must be for just beginning to carry out or dynamically carry out in operation when disposing.Channel optimization procedures 200 WLAN (WLAN) of can arranging in pairs or groups is used (for example according to IEEE 802.11) and is carried out.

As shown in Figure 2, channel optimization procedures 200 starts from step 205.Channel optimization procedures 200 dynamically determines best operation channel in the normal system operation, can not allow the interior relevant WTRUs of BSS be exposed to a service disruption.In step 210, AP 105 regularly with each channel in the middle of the short time scanning plurality of channels avoiding that its associated user is caused service disruption, and measure at these channels.In step 215, if through judging that AP is just in a low duty cycle that is do not have the BSS traffic and/or operate during not having the associated user, this channel optimization procedures of AP 105 primings judges whether that by the mode of " expect channel loading " of calculating each channel during a high system load take the measured value of obtaining as the basis a new channel can be more suitable for (step 220).In step 225, AP 105 changes its operation channel into possess minimum expectation channel loading channel.

In current IEEE 802.11 networks, do not allow the relevant WTRU 110 operation channels of AP 105 notices that one mechanism (not having in basic standard at least) that changes is arranged.If an AP 105 changes channels, its each relevant WTRUs 110 finally will appreciate that and has lost and the communicating by letter of AP 105, and finally can begin to search a new AP.It probably reselects this AP at the new operation channel of same AP.In any case problem is that WTRUs can feel a service disruption in just newly channel and this AP contact again from its forfeiture to it in the communicating by letter of AP.For avoiding service disruption, channel optimization procedures 200 can be waited until and just change channel when not having traffic in the BSS (cell).On the other hand, some versions in the middle of IEEE 802.11 standards (being the future version that IEEE 802.11h reaches this standard that probably has) may allow AP to hand over letter to inform the change channel to its WTRU.In this case, channel optimization procedures 200 not necessarily will not have the BSS traffic just to carry out by the time.Therefore, as long as channel optimization procedures 200 is able to periodic operation and has just to change the operation channel.

In all situations, a sequence of channel optimization procedures 200 scanning channels (for example one of channel 1-11 tabulation) is to detect available optimum channel.This channel can be according to a predefined procedure and is scanned, and perhaps this channel can be randomly and is scanned.That scan channel is not have to begin in the BSS traffic at this emphasis that will emphasize.Scan channel is implemented continuously in the normal operation whole process of AP 105 and is occured.For instance, AP 105 may just spend 5 milliseconds to listen to a different channels in per 0.5 second.AP may regularly repeat this thing, scans a different channels at every turn.By doing like this, 1% (5 milliseconds of the per 500 milliseconds of usefulness) that AP 105 steals with media time scan other channel, cause minimum impact for the associated user.Channel sequence not necessarily will comprise all available channels.Be recorded in the information relevant with each AP that detects on each channel.This information can be including (but not limited to) in the identity that is scanned other APs that channel operates, and other APs is the indication of the part of same ESS whether, the signal strength signal intensity of APs, and the traffic amount on the channel, and whether any other interference source is arranged on the channel.

Be scanned channel for each, this process is judged: 1) have which other APs to operate at this channel; 2) this APs part (that is according to ESS) of same system whether; 3) signal strength signal intensity of this APs; 4) the traffic amount on this channel; And 5) whether any other interference source (for example non-802.11 disturbing) is arranged on this channel.Traffic amount on the channel is normally measured with regard to the channel utilization rate, and this channel utilization rate is equivalent to receiver by the time percentage of WLAN signal carrier locking.

Scanning is regularly and constantly to occur.In case the channel optimization procedures is triggered (that is not having BSS traffic and/or associated user, perhaps is merely a regular trigger mechanism, for example per 5 minutes), AP 105 judges which channel provides best efficiency.For instance, this may be by measure which channel have minimum interference or other APs whether the mode of the part of same ESS judge.This other APs that inspection measures whether same system a part and decide, AP can determine for the selection of using channel more positive or more not positive.

In an alternate embodiment, coordinate frequency is selected and can be finished by following mode: 1) make APs mutually exchange the information of relevant its speciality (for example load, capacity or position); Or 2) centralized architecture that can obtain from each AP the channel of all APs in information and the setting network is arranged.With regard to the first situation, each AP still can independently make decision, but the information of exchange can allow one better to determine (for example its can comprise be difficult to by another AP from external observation to statistics).With regard to the second situation, to collect information and notify a centralized unit or device with this information from different APs, this centralized unit is made a decision and is later notified different APs with this decision after receiving information.

Channel optimization procedures 200 is performed as and selects an optimum channel (a for example low load channel) when a present channel just is being used.Channel optimization procedures 200 can be triggered by one of them condition of following condition: the time of origin of 1) carrying out the selection of optimization channel last time is T at least _LastBefore second; 2) in the WTRUs that does not have at present to contact with AP; Or 3) at nearest T _FreeAll there is not the BSS traffic with the AP contact in second.Accordingly, T _LastThat priming last time from any channel selection procedure is to the minimum lapse of time that will trigger channel optimization procedures 200; And T _FreeTo be sent to or to transfer to from the BSS package of AP the minimum lapse of time that will trigger channel optimization procedures 200 from last time.

Before triggering the selection of optimization channel, have at least T by in aforementioned trigger condition, guaranteeing _FreeThe WTRUs that does not have the BSS traffic second and not do not contact with AP 105 at that time, channel optimization procedures 200 can not interrupt any data of sending outside and shift for example that sound incoming call, network are downloaded and/or FTP shifts.On the other hand, if there is way to allow relevant WTRUs 110 channels of AP 105 notice that one variation is arranged, optimization channel selection procedure 200 can regularly operate and needn't wait the BSS traffic and do not exist.

Fig. 3 A and Fig. 3 B connect together, and it is a detail flowchart according to a channel optimization procedures 300 of the present invention.Channel selects optimization 300 to comprise four subprocess: a 1) measuring process 305; 2) a candidate channel decision process 310; 3) channel selection procedure 355; And 4) a channel renewal process 380.

In measuring process 305, calculate the average load of each contiguous BSS

In one embodiment, the regularly load of each contiguous BSS of estimation of measuring unit 135.If any load estimated value of a BSS is greater than L _MIN, the load of the contiguous BSSs of all that then should the estimation cycle is charged in the memory 150.If all BSSs have less than L _MINThe load estimated value, then ignore these load estimated values.The load estimated value N that only keeps most recent in the memory 150 _{Load_est}Set.

According to preferred embodiment, AP 105 listens to the particular channel of an ACS quiet measuring period (SMP) at each.AP 105 is listening to each channel in the SMPs in succession in turn, and measures an other measuring assembly of each channel in the ACS.Measuring assembly contain with ACS in the as many SMPs of channel quantity.In a known SMP, measured the channel utilization rate (CU) of channel by measuring unit 135.CU is equivalent to transceiver 125 by the time percentage of carrier lock.Owing to observe CU during a SMP, all packages that cause AP 105 carrier locks are to be derived from contiguous BSSs.The CU measured value is representing BSS outer channel utilization rate.Process indivedual CU measured values and record the average BSS load of one of BSS in order to obtain each

The BSS IDs that it is also noted that all BSSs on the channel can go on record together with each channel utilization rate measured value.

Only there is the high capacity measured value to be recorded in order to avoid unnecessary course record (logging).The course record is equivalent to record or the storage of measured value.As described in a little earlier, channel optimization procedures 300 is not only having operation in the BSS traffic (that is not being loaded).For reducing the quantity of record measured value, channel optimization procedures 300 is the high capacity measured value of storing predetermined quantity only.

CU is less than C _MINMeasured value to be excluded in order to guarantee the channel optimization be as the basis take the measured value obtained under a remarkable system load state.In other words, if the CU measured value that presents in a measuring assembly has any greater than C _MIN, then record this whole measuring assembly.On the other hand, all channels all are CU＜C _MINMeasuring assembly then be omitted.Measuring assembly can be the BSS IDs of all BSSs on the CU of each channel and the channel.

Channel optimization procedures 300 determines the optimum channel of its own BSS as the basis take separate channel utilization rate measured value.Though the channel optimization should be take the measured value obtained under remarkable system load state as the basis, channel optimization procedures 300 only also can be in system load and carries out in having alleviated.For avoiding huge measurement course record, only has the measurement window N of most recent _SETBe retained in the memory.

Refer back to Fig. 3 A, in measuring process 305, the average load take indivedual loads of a BSS as each BSS of basic calculation.The momentary load of the BSS i that operates in channel k during measuring assembly j is take equation (1) as the basis:

$L(i,j)=\frac{C(k,j)}{N_{\mathrm{BSS}}(k,j)}$

Equation (1)

Wherein C (i, j) representative is at channel utilization rate and the N on channel k during the measuring assembly j _BSS(i, j) represents the quantity of BSSs.The average load of BSS i is calculated as the mean value that all are recorded the momentary load in the measuring assembly according to equation (2):

$\stackrel{\‾}{L}\left(i\right)=\max [1\%,\frac{1}{N_{\mathrm{SET}}}\underset{j=1}{\overset{N_{\mathrm{SET}}}{\mathrm{\Σ}}}L(i,j)]$

Equation (2)

N wherein _SETRepresentative is recorded the total quantity of measuring assembly.Add 1% minimum average B configuration BSS load.The method of calculating the average load of each BSS is not limited to above-mentioned example.

The example parameter that substitutes metering system is listed in the table below 2.The personnel that are familiar with this skill will appreciate that and can also use other parameter and numerical value or replace with other parameter and numerical value outside these parameters and numerical value.

Table 2

In candidate channel decision process 310, AP 105 retrieval maximums are allowed interference I _MAX(step 315), it is for allowing interference take the baseline scope of an AP as the maximum that the basis determines on any known channel.Better, for the I of candidate channel decision process 310 _MAXTo calculate according to equation (3):

I _MAX＝P _MAX-(RNG _base+RNB _adj)-(C/I) _{req_high}-M _I

Equation (3)

(RNG wherein _Base+ RNG _Adj) be the scope that AP 105 covers; And (C/I) _{Req_high}Be set to the necessary carrier power interference ratio of a two-forty package (for example 11Mbps).Deduct an enough and to spare M _IPossesses the possibility of too allowing the interference level that the position is accurate near actual maximum to eliminate channel.

Select one first channel (step 320) from an ACS.Then measure the interference I of this channel and allow interference I with itself and maximum _MAXCompare (step 325).If allowing less than maximum, the interference I of this channel disturbs I _MAX, then AP 105 charges to a candidate list (step 330) in the memory 150 with this channel.If being not less than maximum, this channel disturbance I allows interference I _MAX, then AP 105 checks in the ACS whether also have any channel to have (step 335).If still there is channel to exist in the ACS, then AP 105 selects next channel (step 340) and process 300 is got back to step 325 from ACS.If no longer include channel in the ACS, then AP 105 checks whether any available candidate channel (step 345) is arranged.If judging in step 345 does not have the available candidate channel, then AP 105 is with I _MAXIncrease Δ dB (step 350), and channel optimization procedures 300 is got back to step 320.If in step 345, judge to have at least a candidate channel to exist, then carry out channel selection procedure 355, shown in Fig. 3 B.

Channel selection procedure 355 is the average loads that record BSS with each

And present BSS-channel reflection β (k).All channel calculation are gone out one expect channel utilization rate C _PRED(k) (step 360).C _PRED(k) representative is used to expect the channel utilization rate from the channel k that the load estimated value of high load condition is expected.C _PRED(k) may be totally different in the most recent channel utilization rate measured value of channel k.Better for C _PREDBut not only utilize most recent channel utilization rate measured value to be basic selective channel, because the channel selection should be for the high load condition optimization.

With regard to each channel k, upward all record the average load of BSSs to add total channel k according to equation (4):

$C_{\mathrm{PRED}}\left(k\right)=\underset{\∀i\∈\mathrm{\β}\left(k\right)}{\mathrm{\Σ}}\stackrel{\‾}{L}\left(k\right)$

Equation (4)

In case calculate the C of all candidate channel _PRED, select to possess the minimum channel k that expects the channel utilization rate according to equation (5):

K=arg _kMin[C _PRED(k)] equation (5)

This moment, whether AP 105 inspection selective channel k were different from a present channel (step 370).Be same as present channel if possess the selective channel k of minimum expectation channel utilization rate, then channel selection procedure 355 finishes.If selective channel k is different from present channel, then it judges whether change channel has obvious interests (step 375).One hysterisis criterion

Guarantee to change channel and have enough large interests.In particular, so long as conform with the new channel of following condition and will be used:

$C_{\mathrm{PRED}}(\mathrm{Current}\_\mathrm{channel})-C_{\mathrm{PRED}}\left(K\right)>H_C^{\mathrm{Opt}}$ Equation (6)

Otherwise just finishing the optimization channel selects.

The example parameter that the optimization channel is selected is listed in the table below 3.Person skilled in the art person will appreciate that and can also use other parameter and numerical value or replace with other parameter and numerical value outside these parameters and numerical value.

Table 3

One better simply channel selection algorithm may be only according to the channel utilization rate measured value (that is being chosen in the channel that observes the lowest channel utilization rate under the high load condition) that record is arranged.But, the front situation that has changed the operation channel that contiguous APs selects at a known AP priming optimization channel probably occurs.There is the CU measured value of record can't accurately express channel loading within the next high capacity cycle.Therefore, channel selects system with one of channel utilization rate expectation value C _PREDBe the basis, and C _PREDSystem videos as the basis take the BSS-channel of estimating BSS load and most recent.

In case channel selection procedure 355 is finished, if select a new channel then utilize a channel renewal process 380 to upgrade the BSS channels.In channel renewal process 380, judged whether that any WTRUs 110 contacts (step 385) by present operation channel and AP 105.If like this, AP 105 at first must remove each relevant WTRU 110 transmission one and concern message (step 390).Then AP 105 changes its operation channel into new channel (step 395).If there is not WTRUs 110 to contact by present operation channel and AP 105, then AP 105 changes its operation channel into new channel.

Goodly carried out channel optimization procedures 300 from last time and start at and pass through at least T _LastSecond.Otherwise just ignore trigger criteria.Therefore, T _LastValue can be identical with the value of channel optimization procedures 300.In case start at from channel-changing and to pass through T _Last, i.e. every T _MEASAssess termly two trigger conditions.

Although with regard to particular combinations feature of the present invention and assembly are described in preferred embodiment, each feature or assembly must be used alone or use with the multiple combinations that is with or without further feature of the present invention and assembly.

Claims (9)

1. access point comprises:

Measuring unit, described measuring unit are configured for the job parameter of measuring each channel of tolerable channel set when starting described access point; And

Channel selector, described channel selector is configured for the different channel of present operation channel of selecting to use from described access point, communicate with a plurality of wireless transmission/receive units being used for, wherein said channel selector is determined candidate channel based on measured job parameter, and selects new operation channel by carrying out following optimization channel selection procedure from described candidate channel:

Calculate the expectation channel utilization rate that is used for all candidate channel;

From described candidate channel, select to have the minimum channel of expecting the channel utilization rate;

Whether the described channel of determining to have the described minimum selection of expecting the channel utilization rate is different from described present operation channel; With

Under the condition different from described present operation channel of the selected described channel with described minimum expectation channel utilization rate, determine whether the channel utilization rate of described present operation channel expects that than having described minimum the channel utilization rate of the selected described channel of channel utilization rate has more predetermined threshold at least

Wherein, described access point will be removed related with any the described wireless transmission/receive unit that is associated with described access point by described present operation channel, described minimumly expect that the described channel utilization rate of the selected described channel of channel utilization rate has more described predetermined threshold at least to respond the described channel utilization rate of determining described present operation channel than having.

2. access point according to claim 1, wherein said measuring unit and described channel selector are merged in the integrated circuit.

3. access point according to claim 1, described access point also comprises:

Memory, described memory are configured be used to storing measured described job parameter.

4. access point according to claim 1, wherein said measuring unit is measured the average load of detected each contiguous basic service set on channel, and this channel selector detected interference level on the described candidate channel is selected candidate channel and selected new channel as the basis take described average load from described candidate channel as the basis.

5. access point according to claim 4 wherein, is allowed less than the maximum on the described candidate channel at the interference level of described candidate channel and to be selected described candidate channel under the condition of interference from described tolerable channel set.

6. access point according to claim 1, wherein, under the condition identical with described present operation channel of the selected described channel with described minimum expectation channel utilization rate, perhaps, described channel utilization rate at described present operation channel does not have more under the condition of predetermined threshold at least than the described channel utilization rate of the selected described channel with described minimum expectation channel utilization rate, and then described optimization channel selection procedure finishes.

7. one kind is used for selecting at least one optimum channel for the method for the access point use with at least one operation channel, and described method comprises:

Determine a plurality of candidate channel by described access point use;

By carrying out following optimization channel selection procedure from described a plurality of candidate channel selective channel with as new operation channel:

Calculate the expectation channel utilization rate that is used for all candidate channel;

From described a plurality of candidate channel, select to have the minimum channel of expecting the channel utilization rate;

Determine selected have describedly minimum expect whether the channel of channel utilization rate different from present operation channel;

Have under the minimum channel of expecting the channel utilization rate condition different from described present operation channel selected, determine that whether the channel utilization rate of described present operation channel has more predetermined threshold at least than the channel utilization rate of the selected described channel with described minimum expectation channel utilization rate; With

Remove related with any wireless transmission/receive unit that is associated with described access point by described present operation channel, have more at least described predetermined threshold to respond the channel utilization rate of determining described present operation channel than the channel utilization rate of the selected described channel of the channel with described minimum expectation channel utilization rate.

8. method according to claim 7, described method also comprises:

The average load of each that calculate that a plurality of contiguous infrastructure services concentrate; With

The record average load is greater than the information of the contiguous basic service set of threshold value.

9. method according to claim 7, wherein, under the condition identical with described present operation channel of the selected described channel with described minimum expectation channel utilization rate, perhaps, channel utilization rate at described present operation channel does not have more under the condition of predetermined threshold at least than the channel utilization rate of the selected described channel with described minimum expectation channel utilization rate, finishes described optimization channel selection procedure.

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